Rotary basket processing apparatus



Feh. 18, 1969 C- WENZEL ET AL ROTARY BASKET PROCESSING APPARATUS Filed April 5, 1967 INVENTORS CHARLES WENZEL HOWARD If. FQ/OMA/V United States Patent 5 Claims ABSTRACT OF THE DISCLOSURE A rotary basket chemical processing arrangement is adapted to batch process subject work pieces in a flexible and uniform manner. The basket includes a removable section for easy accessibility, and a plurality of separators having projections thereon to inhibit awork surface masking surface tension action.

This invention relates to an arrangement for processing work pieces and, more specifically, to a compartmentalized rotating basket apparatus for chemically treating subject work elements.

Many applications of present day interest require relatively thin, fragile, semiconductor elements having cleaned, etched and/or highly polished critical surfaces. To effect such operations, typical prior art mechanical finishing organizations utilize a friction mechanism employing polishing cloths of paper, felt, pitch, or the like. This has often proven unsatisfactory, however, as not being amenable to batch processing, and as also giving rise to unacceptable internal stresses in the semiconductor wafers causing bowing therein.

When chemical processing has heretofore been employed, large surfaces of the work pieces have adhered to the containing apparatus through surface tension interaction. Accordingly, such surfaces have not been processed in a desired uniform manner since they have not been fully exposed to the active chemical bath for significant processing intervals. Moreover, the waste materials exuded from the surface of such chemically treated wafers have typically been circulated by the bath to come in contact with the surfaces of other work elements, thereby preventing the proper chemical treatment of said surfaces.

It is therefore an object of the present invention to provide an improved apparatus for finishing work pieces.

More specifically, an object of the present invention is the provision of an improved rotary basket processing organization for chemically imparting uniform properties to work element surfaces.

These and other objects of the present invention are realized in a specific illustrative finishing apparatus which includes a perforated cylindrical basket having a removable section. The basket is functionally divided into a plurality of contiguous compartments by a plurality of regularly spaced separators. The separators are characterized by a cross-like geometry which restricts liquid flow between compartments, and include inward projections to inhibit adhesion of work pieces thereto through surface tension action. The basket assembly is selectively insertable in a main frame which, in turn, may be inserted in a trough containing a chemical bath. The frame includes a motor and a gearing arrangement for rotating the basket in the trough.

To effect a cleaning, polishing, etching, washing or other finishing operation, the basket section is removed, and work pieces, e.g. semiconductor elements, are placed in the basket compartments. The section is then replaced, the composite main frame inserted in the desired chemical bath solution, and the basket rotated by the motor and gears to effect the desired finishing operation.

A complete understanding of the present invention and of the above and other objects and features thereof may be gained from a consideration of an illustrative embodiment thereof depicted in the accompanying drawing, in which:

FIGURE 1 is an exploded view of a composite rotary basket finishing organization embodying the principles of the present invention; and

FIGURE 2 depicts the particular configuration characterizing a plurality of separators 20 employed in the arrangement of FIGURE 1.

Referring now to FIGURE 1, there is shown an illustrative rotary finishing organization which includes a perforated basket 10 having a removable section 12. The section 12 is selectively secured to the basket 10 by two chemically inert end 0 rings 11 which may advantageously be fabricated of Teflon (a trademark of the du Pont Corporation for polytetrafiu-oroethylene).

The basket 10 includes a plurality of regularly spaced separators 20 having a structure more particularly shown in FIGURE 2. Each sepai ator 20 is of a general cross-like geometry having a central aperture 22 therein, and also including a plurality of surface tension adhesion eliminating projections 23 thereon.

At either end of the basket 20, and concentric therewith, are cylindrical rods 13 which are insertable in split bearing blocks 14. Each pair of blocks 14, in turn, is secured together by two screws 15.

One bearing block 14 of each pair is mounted on a main frame 30 having a motor 35 thereon. The motor 35 is coupled to a driving gear 40 which engages a driven gear 41 mounted adjacent to one end of the basket 10. It is noted at this point that the entire basket, frame and gearing assembly may advantageously be fabricated of a corrosion-resistant polyvinylchloride (PVC) material.

To effect a finishing operation, the screws 15 are removed thereby unse'curing the split bearing blocks 14. The composite basket assembly is removed, and the 0 rings 11 are slipped to the end of the basket 10 thereby freeing the section 12 which is removed. The basket 10 may then be filled with wafer elements, one per compartment between each two contiguous separators 20. The section 12 is replaced and secured by the 0 rings 11, and the entire filled basket assembly is remounted on the main frame 30. The frame is then inserted in a trough 28 containing 'a chemical cleaning, etching, polishing, washing or other finishing bath,

When the motor 35 is energized it drives the gears 40 and 41, thereby rotating the basket 10 in the bath solution to effect the desired chemical processing. Since the projections 23 inhibit the work pieces from adhering to the sides of any separator 20 under surface tension action, all surfaces of the wafers are uniformly, completely and continuously exposed to the active solution. There is only edge contact between the subject wafers and the basket as the wafers undergo a gentle tumbling action as the composite basket 10 rotates.

The edges of the cross-shaped separators 20 have been found to keep the liquid bath flow between wafer processing compartments at a low level. The general flow of the bath in the areas abutting the wafer surfaces is radially outward through the [basket perforations, thereby carrying the wafer surface waste products and the heat generated by chemical reaction in such a direction. Accordingly, such waste materials are not transported by the locally heated bath from wafer compartment, which would impart an undesirable scratching action to such wafers there located.

When the finishing operation is completed, the frame 30 is lifted from the trough 28, and the basket 10 is removed. A new basket filled with other work pieces may then be inserted to initiate batch processing anew. Alternatively, the basket containing the elements previously operated upon may be transported along with its associated frame 30 to a trough 28 containing a new bath solution (of the same or different composition) for additional processing. When all operations on the waters are completed, they are removed from the basket by removing the section 12.

Thus, the rotary chemical finishing organization of FIGURE 1 has been shown by the foregoing to batch process semiconductor or other work elements in a simple, reliable, uniform and flexible manner.

It is to be understood that the above-described apparatus is only illustrative of the application of the principles of the present invention. Numerous other arrangements and modes of operation may be devised by those skilled in the art without departing from the spirit and scope of the invention. For example, the perforations in the basket 10 may be replaced by slots to effect ultrasonic finishing of the work pieces.

What is claimed is:

*1. In combination in a chemical processing organization, a work piece containing a basket having a plurality of perforations therein, a selectively removable section included in said basket, means for selectively securing said section in said basket, a plurality of regularly spaced separators included in said basket dividing said basket into a plurality of chambers, at least one projection on each of said separators and projecting into the adjacent chamber, a main frame, means for selectively mounting said basket on said frame, and means for rotating said basket.

2. The combination as in claim 1 wherein said separators comprise a cross-shaped geometry.

3. The combination as in claim 1 wherein said removable basket section securing means comprises two end 0 rings.

4. The combination as in claim 3 wherein said basket rotating means comprises a driving gear, a motor coupled to said driving gear, and a driven gear mounted concentrio with said basket and coupled to said driving gear.

5. The combination as in claim 4 wherein said basket mounting means comprises a split bearing block.

References Cited UNITED STATES PATENTS 640,428 1/ 1900 Sterling 134-159 2,099,121 11/1937 Kivley 134-140 2,116,753 5/1938 DinetZ 134-140 FOREIGN PATENTS 488,130 7/ 1938 Great Britain.

ROBERT L. BLEUTGE, Primary Examiner.

US. Cl. X.R. 

